The present invention relates to a method for generating synthetic audio signals through the use of a synthesizer.
Methods of this kind are mainly used in mobile terminals, such as third generation mobile radio terminals, to generate ring tones.
For the generation of synthetic audio signals with the aid of a music synthesizer embodied in software, the computing expense required is approximately proportional to the sampling rate of the output signal. Because of the Nyquist condition, the output signal may contain frequencies only up to half the sampling rate. If, however, the sampling rate is reduced to lower the computing power required, high-frequency signal components are no longer reproduced. In this case, the signal sounds unnatural and muffled.
If a synthesizer of this kind is used, for example, to generate ring tones in mobile telephones, the reduction in the sampling frequency also has the effect of reducing the perceived loudness of the ring melody and, thus, of reducing the signal effect.
Because very inexpensive processors are used for synthesizers in the consumer field (e.g., mobile telephones, electronic games) to save costs, the available computing power is always very scarce. Expensive processors with very high computing power are used for high performance synthesizers. Such processors are both too expensive and too large, and also require too much current, for mobile telephones and electronic games.
Mobile telephones, for example, use special integrated circuits (ICs) (for example, MA-2 from Yamaha), that require a minimum current and chip area at a relatively high sampling rate. Such ICs are expensive and require additional space on an associated circuit board. There is also the cost of production and testing.
For many mobile telephones, the number of tones that can be played simultaneously is reduced in order to lower the computing power required. The disadvantage of this however is that it is not possible to reproduce complex melodies because not all the tones to be played can be reproduced at the same time.
An object of the present invention is, therefore, to provide a method for generating synthetic audio signals through the use of a synthesizer, thus enabling the computing power required to be minimized with, at the same time, sound of the synthesizer being impaired as little as possible.